EVALUATION OF METHODS FOR CALCULATING CENSUS HEALTH INDICATORS FOR GPPRACTICES

The patients registered with a general practice are usually spread ove r many census areas and overlap with the distribution of neighbouring practices, so a validated method of aggregating census data to describ e the characteristics of practice patients is required. Four methods w ere used to provide estimates of the percentage of patients aged 75 ye ars and over from census data for 81 practices in Suffolk, England, an d these were compared with values derived from the FHSA patient regist er. Census values for practice areas produced better estimates than th ose based on the location of the surgery, but the best methods were ba sed on patient-weighted averages of ward and enumeration district data . The finer geographical detail of enumeration districts did not produ ce substantially more accurate estimates than the ward-level data: bot h gave estimates with limits of agreement within 2% of the patient reg ister values. Errors in the census, errors in patient registers and se lective geographical distributions of practice patients prevent close matching of census and register measures, but two of the methods teste d produced estimates that allow broad comparisons between practices.